Unique Itinerant Ferromagnetism in 4d-electron System Ca2RuO4

We have studied the magnetic properties of pressure-induced ferromagnet Ca2RuO4 to reveal the uniqueness of the 4d-electron ferromagnetism in the quasi-two-dimensional conductor. The magnetic parameters have been estimated from the paramagnetic susceptibility and the magnetisation process under pressure up to 2 GPa. The parameters can well be interpreted on the basis of the self-consistent renormalization theory of spin fluctuation for 3D-itinerant ferromagnet. Nevertheless, the metallic Ca2RuO4 shows quite strong anisotropy not only in the conductivity but also in the magnetisation process. Such the strong anisotropy is rare for an itinerant ferromagnet and is a unique characteristic of the 4d electron system Ca2RuO4.